U.S. Pat. No. 3,426,006 discloses tin containing organo-metal initiators made by reactions from 1 mole of stannous chloride with 3 moles of alkyl lithium (column 5, lines 29-38). These initiators are then used to form colorless polymers. This initiator type has been shown by Tamborski et al., Journal of Organic Chemistry, Vol. 28, page 237 (1963) to be predominantly an equilibrium mixture of dibutyltin and butyl lithium wherein the butyl lithium is the more active initiator and hence, only of a few of the polymer chains produced from its initiation actually contain tin atoms.
U.S. patent application Ser. No. 07/636,961 filed Jun. 2, 1991, which is published European Application 493839 of Jul. 8, 1992, discloses several alternate ways to make triorgano substituted-tin lithium initiators and their use to make organotin terminated polymers with reduced hysteresis. The initiators disclosed therein had higher residual ionic chloride concentration than claimed herein or were made with a more expensive distillation process which results in undesirable tetrabutyltin and/or tributyltin hydride impurities.